Abstract: Field plot and micro-plot experiments were conducted to investigate the use efficiency (UE), fate, and loss of chemical fertilizer N in tomato field of Nanjing suburb. The results showed that the application of chemical fertilizer N did not show any benefit to the tomato yield, due to the adequate N supply from native soil and organic manure amendment. The UE of fertilizer N calculated by difference method ranged from 14.5% to 22.5%. In micro-plot experiment, 16.6%～28.8% of applied urea ¹⁵N was recovered by the plant, and 34.2%～46.0% of it was lost. Applying fertilizer N increased the nitrate content in 0～100 cm soil layer, and 10%～10.2% of urea ¹⁵N was leached to the depth below 40 cm at harvest time. N application increased the denitrification loss and N₂O emission significantly, which occupied 5.50%～6.01% and 2.62%～4.92% of the applied N, respectively. No ammonia volatilization was detected during the whole growth season. Reducing N application rate or applying coated urea could decrease the environmental risks of N application in vegetable fields, especially the risks from nitrate leaching and nitrification-denitrification loss.

Key words: Pollen germination, Tube growth, Ultraviolet B(UV-B)radiation